This invention relates generally to the generation of gas such as used in the inflation of automotive safety restraint airbag cushions and, more particularly, to gas generant compositions containing copper ethylenediamine dinitrate and associated methods of gas generation.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an xe2x80x9cairbag cushion,xe2x80x9d that is inflated or expanded with gas such as when the vehicle encounters a sudden deceleration, such as in the event of a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system, the cushion begins to be inflated in a matter of no more than a few milliseconds with gas produced or supplied by a device commonly referred to as an xe2x80x9cinflator.xe2x80x9d
Many types of inflator devices have been disclosed in the art for use in the inflating of one or more inflatable restraint system airbag cushions. Many prior art inflator devices include a gas generant material having a solid form and which is burned to produce or form gas used in the inflation of an associated airbag cushion.
Gas generant compositions commonly utilized in the inflation of automotive inflatable restraint airbag cushions have previously most typically employed or been based on sodium azide. Such sodium azide-based compositions, upon initiation, normally produce or form nitrogen gas. While the use of sodium azide and certain other azide-based gas generant materials meets current industry specifications, guidelines and standards, such use may involve or raise potential concerns such as involving the safe and effective handling, supply and disposal of such gas generant materials.
Further, such inflator devices tend to involve ignition assemblies and processes which are either or both more complex and costly than desired. For example, airbag inflator ignition systems commonly involve first the ignition of an electrically ignited squib, which in turn ignites a supplemental secondary ignition charge, which finally ignites a quantity of a gas generant composition contained therewithin. Since the secondary igniter charge usually involves the use of expensive energetic ingredients (i.e., boron) and may impose expensive processing restraints or limitations (such as production of limited quantities due to safety constraints and containerization), there is a need for simple and effective alternatives to such ignition systems.
A common alternative means of obtaining substantially simultaneous ignition of an extended length of igniter composition charge is through the incorporation of an ignition cord within an inflator. In practice, it is common that such length of ignition cord be housed or contained within an igniter tube extending within the igniter charge. While ignition of an associated gas generant material may ultimately be achieved through the incorporation and use of such an ignition cord, such an ignition process may also be undesirably complicated and may also tend to undesirably complicate the manufacture, production and design of the inflator device. For example, such use necessitates that an igniter composition be manufactured or made and then subsequently handled such as through manufacture of a desired form of container to hold or store the igniter composition for subsequent incorporation into the inflator device design as a part of an igniter assembly.
In addition, the use of such an ignition process can detrimentally impact either or both the weight and cost of the corresponding apparatus hardware. For example, the incorporation and use of such an igniter tube and ignition cord typically will undesirably increase both the weight and cost associated with a corresponding assembly.
As will be appreciated, space is often at a premium in modem vehicle designs. Consequently, it is generally desired that the space requirements for various vehicular components, including inflatable vehicle occupant restraint systems, be reduced or minimized to as great an extent as possible. The incorporation of an igniter assembly such as described above and associated support structures, may require a larger than desired volume of space within an associated inflator device. In particular, such volume of space could alternatively potentially be utilized to store or contain gas generant material and thereby permit the volume of space required by the inflator device to be reduced.
Thus, there is a need and a demand for alternative airbag inflator device ignition schemes and, in particular, there is a need and a demand for avoiding the requirement or inclusion of separate igniter composition charges and associated hardware.
At least partially in response to the need for alternatives to inclusion of such ignition systems, substantial efforts have been directed to the formation of ignition enhanced gas generant materials such as involving coating of a gas generant material with an igniter material. While the practice of applying an igniter material as a thin coating directly on gas generant grains is a generally viable approach that has been used in the past, such an approach is subject to certain disadvantages. For example, such a coating process can be subject to variations in coating thickness and effectiveness such as to hinder or prevent attaining desired consistency and uniformity in performance. Further, the costs associated with such processing can detrimentally impact system economics.
In view of the above, there is a need and a demand for gas generant compositions suitable for use in inflate restraint system applications and which compositions are desirably easily ignitable without the use of any secondary igniter or applied igniter coating and which compositions desirably provide relatively high gas yields (e.g., gas outputs of about 3.00 moles or more of gas per hundred grams of composition).
A general object of the invention is to provide improved gas generation and, more particularly, to provide improved gas generant compositions and associated method of gas generation.
A more specific objective of the invention is to overcome one or more of the problems described above.
The general object of the invention can be attained, at least in part, through a gas generant composition which includes between about 1 and about 18 weight percent of copper II bis ethylenediamine dinitrate, between about 5 and about 50 weight percent of a gas generant co-fuel, and between about 40 and about 75 weight percent of a gas generant oxidizer component.
A gas generant composition in accordance with one preferred embodiment of the invention additionally contains or includes up to about 10 weight percent of a gas generant additive such as a bum rate enhancing and slag formation additive such as includes at least one member selected from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, zirconium oxide, zinc oxide, alkali metal salts and alkaline earth metal salts, for example.
The prior art generally fails to provide a gas generant composition of desired ignitability, such as may be used within an airbag inflator without necessitating the incorporation or use of an igniter composition, either as a separate and distinct charge or as a coating such as applied to an associated gas generant material.
The invention further comprehends a gas generant composition which contains or includes between about 5 and about 12 weight percent of copper II bis ethylenediamine dinitrate; between about 5 and about 50 weight percent of a gas generant co-fuel; and between about 40 and about 75 weight percent of a gas generant oxidizer component, wherein the gas generant oxidizer component comprises at least about 15 weight percent of copper diammine dinitrate.
The invention still further comprehends a method of gas generation which, in accordance with one preferred embodiment of the invention involves the step of igniting a composition containing between about 1 and about 18 weight percent of copper II bis ethylenediamine dinitrate; between about 5 and about 50 weight percent of a co-fuel; and between about 40 and about 75 weight percent of an oxidizer component to form reaction products which at least in part are in gaseous form.
As used herein, references to a material, component, compound or the like as a xe2x80x9cfuelxe2x80x9d are to be understood to refer to such material, component or compound as internally containing insufficient oxygen to allow it to fully combust to water, carbon dioxide, nitrogen and/or a corresponding metal oxide or metal without an added oxidizer or oxygen source.
Further, references herein to a material, component, compound or the like as an xe2x80x9coxidizerxe2x80x9d are to be understood to refer to such material, component or compound as internally containing oxygen in a relative amount in excess of that required to allow it to fully combust to water, carbon dioxide, and/or a corresponding metal oxide.
References to a material, composition or formulation as a xe2x80x9cgas generantxe2x80x9d are to be understood to refer to those materials, compositions or formulations which upon combustion generally provide or result in a gas yield or output of at least about 2 moles of gas per 100 grams of material and, preferably, at least about 2.5 moles of gas per 100 grams of material and, more preferably, at least about 3 moles of gas per 100 grams of material. In practice, gas generant materials generally burn at a flame temperature of less than about 2500 K.
References to a material, composition or formulation as an xe2x80x9cigniterxe2x80x9d are to be understood to refer to those materials, compositions or formulations which upon combustion generally provide or result in a gas yield or output of less than about 1.5 moles of gas per 100 grams of material. In practice, igniter materials generally burn at a flame temperature of greater than about 3000 K.
Other objects and advantages will be apparent to those skilled in the art from the following detailed description taken in conjunction with the appended claims and drawings.